Do I need any fasteners or hardware beyond what comes in the box?

The assembly mounts at factory points. Check your vehicle's existing hardware — in most cases you'll reuse what's already there, but have a set of stainless fasteners on hand in case original hardware is corroded or stripped.

Will this work as a direct bolt-in, or do I need to modify the mounting area?

This is designed for factory mounting points with no drilling or cutting. If your factory points are damaged or corroded, minor filing or hardware substitution may be needed — but the fit is stock-level.

What's the LED lifespan, and are the bulbs replaceable?

The LED housing is integrated into the assembly. LED lifespan far exceeds halogen, but if LEDs fail, the entire unit is replaced — individual bulbs are not serviceable.